In many cases, a semiconductor light-emitting element (hereinafter referred to as an LED element unless specifically stated otherwise) is mounted in a face-up fashion or in a flip-chip (also referred to as face-down) fashion on a circuit substrate of a semiconductor light-emitting device (hereinafter referred to as an LED device unless specifically stated otherwise) for packaging. In the face-up mounting, the LED element is placed on the circuit substrate with the electrode side of the LED element facing up, and the electrodes of the LED element are connected to the electrodes on the circuit substrate by wires. On the other hand, in the flip-chip mounting, the LED element is placed on the circuit substrate with the electrode side of the LED element facing down, and the electrodes of the LED element are connected to the electrodes on the circuit substrate by electrically conductive contacts such as bumps.
Since the LED element is directly connected to the circuit substrate by means of bumps or the like, the flip-chip mounting offers the advantages of being able to enhance heat-sinking efficiency and to reduce the mounting area because of the elimination of the need for wires. To improve the light-emitting efficiency of the flip-chip mounting LED element, a reflective layer may be provided on the electrode side as viewed from the light-emitting layer so that the light emitted from the light-emitting layer and directed toward the circuit substrate may be reflected by the reflective layer and caused to emerge from the LED device.
For example, it is known to provide a semiconductor light-emitting element which comprises a semiconductor layer deposited on a crystal substrate and an n-side electrode and p-side electrode for connecting the semiconductor layer to an Si diode device, wherein the p-side electrode includes a reflective layer (for example, patent document 1). The n-side electrode and the p-side electrode have micro-bumps for connecting to the Si diode device.
It is also known to provide a flip-chip light-emitting diode which comprises a semiconductor layer deposited on a transparent substrate and a first electrode and second electrode for connecting the semiconductor layer to a packaging submount, wherein the first electrode includes a metal reflective layer (for example, patent document 2). The first electrode and the second electrode are each connected to the packaging submount via an intermediate layer formed from a solderable material.
Furthermore, it is known to provide a semiconductor light-emitting element which comprises a semiconductor layer deposited on a sapphire substrate and an n-type electrode and p-type electrode for connecting the semiconductor layer to a submount, wherein the n-type and p-type electrodes each include an Al layer (for example, patent document 3). Each of the n-type and p-type electrodes further includes an Au layer that serves as an overcoat electrode for enhancing adhesion to the submount.
Patent document 1: JP H11-191641-A (FIG. 1)
Patent document 2: JP 2006-121084-A (FIG. 3)
Patent document 3: JP 2002-26392-A (FIG. 2)